Strujanje u umirujućim bazenima stepenastih brzotoka
Stilling basin flow for stepped spillways
Докторанд
Ljubičić, RobertМентор
Savić, Ljubodrag M.Чланови комисије
Prodanović, DušanKapor, Radomir
Čantrak, Đorđe
Zindović, Budo
Метаподаци
Приказ свих података о дисертацијиСажетак
Kod preliva visokih brana, umirujući bazeni predstavljaju najčešće korišćeno rešenje za
disipaciju mehaničke energije vode pre njenog ispuštanja u nizvodno rečno korito. Zbog
značaja i visoke efikasnosti, umirujući bazeni detaljno su izučavani, prvenstveno u sprezi sa
glatkim brzotocima. Disipacione sposobnosti umirujućih bazena mogu se poboljšati
upotrebom različitih stabilizacionih elemenata, čiji efekti omogućavaju smanjenje dužine
hidrauličkog skoka, odnosno gabarita bazena. Slični efekti mogu se postići i promenom
podužnog nagiba dna bazena.
Razvoj tehnologije valjanog betona pospešio je primenu stepenastih brzotoka, koje (u odnosu
na glatke) odlikuje bolja disipacija mehaničke energije. Međutim, uslovi strujanja koji pritom
nastaju – intenzivnije mešanje vode i vazduha, praćeno povećanjem dubine – bitno se
razlikuju od onih koji su poslužili pri razvoju preporuka za tipske bazene sa stabilizacionim
elementima. Iako tipski bazeni i u slučaju stepenastih brzotoka mogu pojačati disi...paciju
energije, njihovi efekti su slabiji od očekivanih. Zbog toga je od posebnog značaja procena
uticaja gabarita i položaja stabilizacionih elemenata tipskih bazena koji su namenjeni za
glatke brzotoke, na disipaciju energije u bazenima stepenastih brzotoka.
Ovo istraživanje posvećeno je ispitivanju uticaja koji stepenasta kontura brzotoka ima na
efikasnost disipacije mehaničke energije u umirujućem bazenu. Pri tome, ispitani su bazeni
sa horizontalnim dnom i bazeni sa dnom u negativnom podužnom nagibu i to, sa i bez,
dodatnih stabilizacionih elemenata. Ocena kvaliteta disipacije mehaničke energije sprovedena
je prvenstveno na osnovu rezultata merenja dubina i brzina tečenja, za šta su korišćene
savremene metode beskontaktnog merenja, bazirane na tehnikama obrade slika iz video
zapisa eksperimenta.
Stilling basins are the most commonly used structures for the large dam spillways energy
dissipation. Due to their high efficiency, stilling basins (with the hydraulic jumps) are well
investigated, mainly for smooth spillways. Energy dissipating capabilities of the stilling
basins can be improved with the use of different types of stabilizing elements, which allow
for the reduction of the hydraulic jump length and consequently for the size of the stilling
basin. Similar effect can be achieved by changing the basin bed slope.
Development of the roller compacted concrete technology has encouraged the use of the
stepped spillways which (relative to the smooth spillways) have higher energy dissipation
rate. However, the resulting flow conditions (more intense air–water mixing, coupled with
higher flow depths) differ from those for which the standardized basins with stabilizing
elements were developed. Consequently, the use of standardized basins can increase energy
dissipation, but the eff...ects are lower than expected. Hence, the assessment of the effects of
the dimensions and position of the standardized-basins stabilizing elements for smooth
chutes, on the efficiency of energy dissipation of stepped-spillway basins, is of special interest.
This research concerns the impact that stepped spillway can produce on the energy
dissipation efficiency of the stilling basin. Hence, horizontal and negative slope stilling basins
were investigated, with and without the use of the stabilizing elements. Assessment of the
energy dissipation efficiency is based mainly on the results of depth and velocity
measurements, which were performed using contactless methods, based on image processing
approach.
Results of this investigation indicate that the energy dissipation quality of stepped spillway
stilling basins can be improved using the stabilizing elements for smooth-chute basins, but
with modified dimensions and position, as well as using the negative basin bed slopes.
Therefore, the estimation of the main flow parameters for the basins with stabilizing
elements, and negative–sloped basins is presented. The significance of the research is also
shown through the use and development of state-of-the-art contactless measurement
techniques: (1) Laser Particle Image Velocimetry (Laser PIV) technique was successfully
applied for the estimation of flow velocities downstream of the hydraulic jump roller, and
(2) a novel method for the estimation of the flow depths is presented, based on the image
processing approach. Ultimately, the analysis of the obtained data provided design
recommendations for the stepped-spillway stilling-basin design.